Mass transport induced structural evolution and healing of sulfur vacancy lines and Mo chain in monolayer MoS2

Defects play vital roles in tailoring structures and properties of materials including the atomically thin two-dimensional (2D) materials, and increasing demands are requested to find effective ways to realize the defect engineering, i.e., tuning the defects and thus the materials’ structure–property in a well-controlled way. Herein, we propose a novel method to tune the structures and configurations of one-dimensional (1D) line defects in monolayer MoS2 via mass transport induced structural transformation. By using atomic-resolved annular dark-field scanning transmission electron microscopy (ADF-STEM), we demonstrate in situ that sulfur vacancy line defect can be healed locally into defect-free MoS2 lattice via the desorption of Mo atoms from vacancy lines and adsorption into a moving Mo cluster. Furthermore, directional transport of Mo atoms (or Mo cluster) along the sulfur vacancy lines can induce the formation of Mo chains. Such a mass transport induced defect tuning provides more operational routes for the rational defect designing and property tuning in MoS2 as well as other related 2D materials.